Freestanding strontium vanadate/carbon nanotube films for long-life aqueous zinc-ion batteries

Abstract

Aqueous rechargeable zinc-ion battery (ZIB) is considered to be a potential energy storage system for large-scale applications due to its environmental friendliness, high safety, and low cost. However, it remains challenging to develop suitable cathode materials with high specific capacity and long-term cyclic stability. Herein, we have fabricated freestanding Sr_0.19V₂O₅·1.3H₂O/carbon nanotubes (SrVO/CNTs) composite films with different mass ratios by incorporating SrVO into CNTs network. The synthesized SrVO possesses a large interlayer spacing of 1.31 nm, which facilitates Zn²⁺ diffusion. Furthermore, the SrVO/CNTs composite film with conductive network structure promotes electron transfer and ensures good contact between SrVO and CNTs during the long-term cycling process. As a result, the battery based on the SrVO/CNTs composite cathode with a mass ratio of 7:3 delivers a specific capacity of 326 mAh·g⁻¹ at 0.1 A·g⁻¹ and 145 mAh·g⁻¹ at 5 A·g⁻¹, demonstrating a high capacity and excellent rate capability. Remarkably, the assembled ZIB shows good capacity retention of 91% even after ultra-long cycling for 7500 cycles at a high current rate of 5 A·g⁻¹. More importantly, the battery also delivers a high energy density and power density, as 290 Wh·kg⁻¹ at 125 W·kg⁻¹ (0.1 A·g⁻¹), or 115 Wh·kg⁻¹ at 6078 W·kg⁻¹ (5 A·g⁻¹). The results demonstrate that the SrVO/CNTs composite is a promising cathode toward large-scale energy storage applications.

Graphic abstract

摘要

水系锌离子电池 (ZIB) 因其环保、安全、成本低等优点, 是一种极具前途的大规模储能设备。 然而, 开发高比容量和高循环稳定性的正极材料仍然具有挑战。 通过抽滤方法将 Sr_0.19V₂O₅·1.3H₂O (SrVO) 和碳纳米管 (CNTs) 复合, 制备了不同质量比的自支撑 SrVO/CNTs 复合膜。 制备的 SrVO 层间距为 1.31 nm, 有利于 Zn²⁺ 的扩散。 此外, 具有导电网络结构的 SrVO/CNTs 复合膜促进电子转移, 并确保 SrVO 与 CNTs 在长期循环过程中的良好接触。 结果表明, 质量比7:3的 SrVO/CNTs 复合膜表现出高存储容量 326 mAh·g⁻¹ (0.1 A·g⁻¹) 和优良的倍率性能145 mAh·g⁻¹ (5 A·g⁻¹)。 同时也实现 5 A·g⁻¹ 下的长期循环稳定性 (7500圈后保留91%的容量) 。 更重要的是, 组装的ZIB显示出高的能量和功率密度, 290 Wh·kg⁻¹/ 125 W·kg⁻¹ (0.1 A·g⁻¹)和115 Wh·kg⁻¹/ 6078 W·kg⁻¹ (5 A·g⁻¹)。 结果表明, SrVO/CNTs 复合材料具有可观的大规模应用潜力。